http://www.legislation.gov.uk/ukpga/1971/24/section/2
Coinage Act 1971
Section 2
Legal tender.
[F1(1)Gold coins shall be legal tender for payment of any amount, but shall not be legal tender if their weight has become less than that specified in Schedule 1 to this Act, or in the proclamation under which they are made, as the least current weight.
(1A)Subject to any provision made by proclamation under section 3 of this Act, coins of cupro-nickel, silver or bronze shall be legal tender as follows—
(a)coins of cupro-nickel or silver of denominations of more than 10 pence, for payment of any amount not exceeding £10;
(b)coins of cupro-nickel or silver of denominations of not more than 10 pence, for payment of any amount not exceeding £5;
(c)coins of bronze, for payment of any amount not exceeding 20 pence.
(1B)Other coins, if made current by a proclamation under section 3 of this Act, shall be legal tender in accordance with the provision made by that proclamation or by any later proclamation made under that section.]
(2)References in [F2subsection (1A)]of this section to coins of any denomination include references to coins treated as being of such a denomination by virtue of a proclamation made in pursuance of section 15(5) of the M1Decimal Currency Act 1969; and silver coins of the Queen’s Maundy money issued before 15th February 1971 shall be treated for the purposes of this section as being denominated in the same number of new pence as the number of pence in which they were denominated.
[F3(3)In this section “coins”means coins made by the Mint in accordance with this Act and not called in by proclamation under section 3 of this Act.]